Good Luck, MTG/Pokemon/YugiOh are HUGE money makers if you have significant clientele in the 10-24 age range (up to 40 for MTG).

This. If I ever did a LCS this would be a staple. They more the better. Actually to add, Legos would also be a staple. Check out my EBay account. Legos are by far and away the best money maker for me. Good Luck!